Available as an assembled Module and as a DIY project.
This Module is currently available.
Specs are approved by the manufacturer3 Channel passive mixer
This simple passive mixer is suitable for mixing both audio and control voltage sources. Three channel inputs mix down to one output.
It is not suitable for additive voltage applications. All the jacks are switched to ground to minimize external interference when not patched. This can lead to unwanted attenuation of the output signal unless you plug a dummy cable into the unused channel(s) or, even easier, you can turn the channel's pot completely CCW.
These merchants probably sell this module. Huh?
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